Common Merganser

Common Mergansers are streamlined ducks that float gracefully down small rivers or shallow shorelines. The males are striking with clean white bodies, dark green heads, and a slender, serrated red bill. The elegant gray-bodied females have rich, cinnamon heads with a short crest. In summer, look for them leading ducklings from eddy to eddy along streams or standing on a flat rock in the middle of the current. These large ducks nest in hollow trees; in winter they form flocks on larger bodies of water.

Typical Voice

Size & Shape

These are large, long-bodied ducks with thin, pointed wings. Their bills are straight and narrow, unlike the wide, flat bill of a “typical” duck. Females have shaggy crests on the backs of their heads.

Color Pattern

Adult males are crisply patterned with gleaming white bodies and dark, iridescent-green heads. The back is black and the bill red. Females and immatures are gray-bodied with a white chest and rusty-cinnamon heads. In flight, both sexes show large white patches on the upperwings (larger in adult males).

Behavior

Common Mergansers dive underwater to catch fish. After the chicks leave the nest in summer, the female stays with them as they grow up while males gather in flocks. In winter, mergansers form large flocks on inland reservoirs and rivers. They stay in these tight flocks to feed and court during the cold months. In migration and winter, they mix with other fish-eating, diving ducks such as Bufflehead, goldeneyes, and other species of mergansers.

Habitat

These ducks live mainly on freshwater rivers and lakes. They are rare in the ocean, but they sometimes use saltwater estuaries in winter. They nest in tree cavities in northern forests near rivers and lakes.

Breeding male

Similar Species

Red-breasted Mergansers are somewhat smaller and thinner overall, with shaggier crests and thinner bills than Common Mergansers. Male Red-breasted Mergansers have reddish markings on the chest where Common Mergansers are clean white. Female Red-breasted are duller overall with less contrasting white on the throat than female Common Mergansers. Hooded Mergansers are much smaller and shorter-bodied than Common Mergansers. Female Hooded Mergansers are gray-brown overall with little contrast between head and body color. Male goldeneyes, both Common Goldeneye and Barrow’s Goldeneye, are also mostly white ducks with dark backs and dark, triangular-shaped heads. Goldeneyes have thick, short bills and white patches on the face.

Backyard Tips

In northern forests Common Mergansers will take up residence in nest boxes near lakes or rivers, as long as the boxes are large with a large opening. Consider putting up a nest box to attract a breeding pair. Make sure you put it up well before breeding season. Attach a guard to keep predators from raiding eggs and young. Find out more about nest boxes on our Attract Birds pages. You'll find plans for building a nest box of the appropriate size on our All About Birdhouses site.

Find This Bird

Common Mergansers are numerous in summer along rivers in northern North America, and many a canoe trip will turn them up without much trouble. Look for them sitting on rocks in midstream, disappearing around the next bend, or flying along the river, when their white wing patches and heavy bodies make them easy to identify. In winter, seek Common Mergansers on large rivers and lakes; look for them in large flocks mixed with other ducks such as Common Goldeneye and Bufflehead. Look for the sharp dark-and-white contrast of the snazzy males and the crisply defined, rusty heads of females.